The invention relates to a closure with pressure-compensating valve for the filling hole of a liquid container, with a bung-type socket of elastic material which fits sealingly into the filling hole and is provided with a central orifice, and with a valve element which can be manually turned into position and which occupies in the central orifice a sealing closed position and a pressure-compensating position, in which the interior of the container is in communication with the atmosphere.
Such a closure is known from German Patent DE 4219571 C2. It has a bung-type socket with alternately larger and smaller axial ventilation grooves along the wall of the central orifice and a valve element with alternately larger and smaller axial ventilation fins along the outside surface. The valve element has closed positions, in which matching grooves and fins are in engagement, and pressure-compensating positions, in which non-matching grooves and fins are in engagement.
When the liquid container is completely filled, the bungtype socket dips with its lower end into the liquid. Actuation of the pressure-compensating valve then has the consequence that liquid emerges from the container. A further disadvantage is that it is difficult to distinguish whether the valve element of the pressure-compensating valve is in one of the plurality of possible closed positions or pressure-compensating positions.